docs: def _coords(shape):
      """
      Return a list of lists of coordinates of the polygon. The list consists
      firstly of the list of exterior coordinates followed by zero or more lists
      of any interior coordinates.
      """
  
      assert shape.geom_type == 'Polygon'
      coords = [list(shape.exterior.coords)]
      for interior in shape.interiors:
          coords.append(list(interior.coords))
      return coords